Acid pickling agent



m. w42. C IL. READ- ,39,3-

A'CID PICK'LING AGENT.

Filed Dec. 17, 1940 ACW PKCKJLING AGENT @Chester L. Read, Westfield, N. JI., assignor t:

Standard Oil Develo poration of Delaware pment Company, a cor- Application December 17, 1940, Serial No. 370,459

(on. cs2- 146) 7 Claims.

'I'he present invention relates to the production of acid pickling agents. The invention is more particularly concerned with an improved process for segregating desired pickling constituents from spent acids utilized in the rening of petroleum oils. In accordance with the present process, spent acids or acid sludgesare treated in a series of stages which treatment comprises hydrolizing the acid sludge, then subjecting the resulting acid phase to a solvent treatment utilizing a solvent having a preferential selectivity for the acid-soluble components of this phase as compared to the acid. These solvent extracted constituents, free of the solvent, are particularly desirable as inhibiting agents for addition to acids to be used in the acid treatment of metals.

It is well known in the art to employ various types of mineral acids in the pickling of steel to remove scale and also to add inhibitors to these acid solutions in order to prevent an excessive loss of the metal. It is also known to employ Weak acids obtained by the hydrolysis of petroleum acid sludges for these pickling operations `since acids of this type contain constituents .which function as corrosion inhibitors.

These petroleum acids may be readily used when the pickling operation is conducted in close proximity to the petroleum refinery operation. However, When the operations are not in close proximity, the transportation charges for transporting the acid are excessive due to the high water content and the fact that the acid must be shipped incorrosion-resistant containers. For this reason, Weak petroleum acids obtained by sludge hydrolysis of spent acids secured in the refining of petroleum oils have not found extensive use in pickling operations.

Various suggestions have been made for overcoming these diiiiculties. It has been proposed that the, inhibitors normally present in these petroleum acids be recovered and then added to the pickling bath When required. For example, one recovery process consisted in completely neutralizing the acidic constituents in order to recover the inhibitors which are insoluble in salt solutions. This processhas several undesirable features, one of which is that the acid is destroyed. Furthermore, the process involves considerable expense due to the large amount of alkaline neutralizing reagent required.

I have now discovered a process whereby these desirable inhibiting agents may be economically and efficiently recovered from dilute spent acids Without any loss ofacid occurring. In fact, the value of the spent weak acid is greatly enhanced since the removal of these inhibitors simplifies the concentrated process and also increases concentrating yields. In accordance with my process, the spent acid or acid sludge is hydrolyzed in an initial stage with water, the .Weak acid phase separated and solvent extracted in a secondary stage with a selective solvent and the solvent extract separated. The extract, after separation of the solvent, is very desirable as an addition agent for acid to be utilized in the pickling of metals.

The process of my inventionmay be readily understood by reference to the-attached drawing illustratingone modification of the same. .A

feed oil whicl'r'for the purposes of description is,

taken to be a petroleum oil boiling in the heating oil boiling range is introduced into acid treating zone I by means of feed line 2. Acid treating zone I may comprise any suitable number and arrangement of acid treating units. In acid treating zone I the oil is contacted with an acid which for the purposes of description is taken to be sulfuric acid which is introduced by means of feed vline 3. The acid treated oil is removed from acid treating zone I by means of line 4, further rened and handled in any manner desirable. .The spent acid lor acid sludge is withdrawn from acid treating zone I by means of line 5 and ishydrolyzed by mixing with a quantity of water.,w'hlch is introduced into the system by means of line 6. The hydrolyzed mixture is introduced into the settling zone k25. The resulting tar phase is withdrawn by line 26 and the acid phase is passed by means of line 21 into solvent treating zone l in which it countercurrently contacts an upflow-ng solvent which is introduced into zone I by means of line 8. For purposes of description, solvent treating zone 'I is shown to be a countercurrent treating system, although it is to be understood that a batch or semi-batch operation may be employed. It is also to be un- .derstood that any suitable method or arrangement of contacting units may be employed. For purposesof description it is assumed that the solvent introduced by means of line 8 comprises monohydroxy phenol. Temperature and pressure conditions are adjusted in countercurrent treating zone l so as to remove by means of line 9 a phenol extract containing the desired pickling constituents. The-solvent treated acid is Withdrawn from countercurrent treating zone I by means of line I0 and further handled or disposed of in any suitable manner. l The phenol extract removed by means of line 9 is introduced into solvent recovery unit 2| which for the purposes of description is shown to be a distillation umt. Temperature and pressure conditions are adjusted to remove overhead by means of line I I the phenol which is preferably recycled to coun.. tercurrent treating zone l. The phenol-removed overhead by means of line II may be removed from the system by means of line I2 in which case fresh phenol is introduced into the system by means of line I3. VThe bottoms product removed from distillation unit 2| by means of line it comprises the desirable constituents of the position introduced into piclling acid storage l by means of line Il.

In accordance with a preferred modification' of the invention, the spent acid removed from the bottom of countercurrent treating zone l by means of line l0 is passed to an acid reconcentration zone l0 by means oi' line I0. Reconcentration zone l0 may comprise any suitable number and arrangements of reconcentration units and related units adapted for the removal of objectionable sludge particles and carbonaceous carbon. Regenerated acid, substantially free of objectionable constituents, is removed from reconcentration zone l0 by means of line 20 and combined with the piclrling agent removed from distillation none it.

The present invention may be widely varied. although the spent acids from which the particular pickling agents of the present invention are secured may be any spent acid secured in the treatment of petroleum oils, it is preferred that these spent acids be secured from acids utilized in the treatment of petroleum oils bol..ng in the range from about 100 F. to 700 F., preferably from those petroleum oils boiling in the heating oil and gas oil boiling ranges. In these operations the feed oils are treated with from about to 20 pounds of 00% to- 98% sulfuric acid per barrel of oil.

Although the present process may be adapted under certain conditions for the treatment of acids of any concentration, particularly desirable resultsare secured providing the spent acid be diluted to a concentration of from to 60%, preferably to about 40% to 50% prior to extracting the same with a solvent, as, for example, a phenol. The preferred concentration will vary to some extent with the solvent used.

Although, in general, solvents selected from the class of solvents which have a preferential selectivity for the relatively more aromatic constituents of a petroleum oil as compared to the relatively more parainic constituents may be used for extracting the spent acid, as, for example, nitrobenzene and beta beta dichlorodiethyl ether, it is preferable to employ phenolic type solvents. The amount of the phenolic type solvent employed to extract the spent acid may vary considerably depending upon the concentration of the acid and the character of the desired pickling constituents and the impurities dissolved in the acid. However, in general, when treating a hydrolyzed spent sulfuric acid having a concentration in the range from about 30% to 60% with a phenol, it is preferred to use from 0.1 to 1.0

volume, preferably from 0.4 to 0.6 volume of phenol per volume of hydrolyzed spent acid. The temperature and pressure conditions, likewise, may vary considerably depending upon operating conditions. In general. it is preferred to employ atmospheric temperatures and pressures.

When employingthe preferred modification of the invention, which comprises regenerating the spent acid after removal of the desirable pickling constituents and thereafter adding said pickling constituents to said regenerated acid, particularly desirable results are secured. Heretofore it has `been impossible to satisfactorily regenerate the acid in the presence of the pickling constituents since degradation of the pickling constituents occurred and, furthermore, since it was aaoasta commercially impossible to remove the undesirm able constituents and to retain the desired pickling constituents in the acid during the regeneration operation.

The inhibitor recovered by this procedure may be added in suitable amount to a mineral acid to be uesd in pickling ferrous metals or alloys for the removal of scale. The mineral acid employed may be derived from any suitable source. The weak acid remaining after the inhibitors are removed may be concentrated to approximately strength, the inhibitors added, and the mixture shipped to the pickling plant.

The pickling solutions normally contain ap" proximately 5% of mineral acid. To a solution of this type, inhibitors recovered by the above described procedure may be added in an amount up to 20% of the mineral acid Weight. In the course of the pickling operation, the acid content of the solution is converted to salts and its effectiveness decreased accordingly. However. fresh concentrated acid may be added to the solution to restore its effectiveness as the inhibitor remains effective for an indefinite period.

In order to further illustrate the invention the following examples are given which should not be construed as limiting the same in any manner whatsoever.

EXAMPLE In order to test the effectiveness of the constituents extracted from spent acid sludge and spentl acids utilizing a selective solvent such as phenol or cresol as corrosion inhibitors, the following operations Were conducted.

Various solutions were prepared having compositions as follows:

Solution Composition 5% H2SO4.

5% 112804+05927 of oil recovered by cresol extraction q! thed separated acid from naphtha and heating oil slu ges.

Corrosion inhibiting properties of constituents extracted with phenol from separated sludge acids Loss in wt.

Solution gq/Sq. cm'

What I wish to claim as new and protect by Letters Patent is:

l. Process for the segregation of pickling constituents, suitable for inhibiting agents in mineral pickling acids, from spent sulfuric acids secured in the refining of petroleum oils boiling in the range from about F. to about 700 F., which comprises hydrolyzing the spent sulfuric acid in an initial stage by the addition of water followed by contacting the hydrolyzed sulfuric acidin a secondary stage with a selective solvent selected from the class of solvents which have a preferential selectivity for the relatively more.

tract phase by the removal of the selective solvent by distillation.

2. Process as defined by claim 1, in which said selective solvent comprises a phenol solvent.

3. Process as dened by claim 1, in which said selective solvent comprises monohydroxy phenol.

4. Process as defined by claim l, in -Which said spent sulphuric acid is secured from a sulfuric acid treatment of a petroleum oil boiling in the heating oil and gas oil boiling ranges.

5. Process as defined by claim 1, in which said spent acid is hydrolyzed to an acid concentration in the range from about 30% to 60%.

6. Process as dened by claim 1, in which the acid sludge is hydrolyzed to a 4concentration in the range from about 40% to 50%.

7. A solution for the pickling of ferrous metals consisting of 2-15% of mineral acid and 0.01-1% of an inhibitor produced in accordance with clai'm 1.

CHESTER L. READ. 

